Sulfur mining using heating by electrolysis



July 30, 1957 w. A. HOYER ET AL SULFUR MINING usmc HEATING BYELECTROLYSIS Filed April 2, 1956 Compressed Air Hot Water nsulutorsMolten Sulphur Sulphur Containing Limestone INVENTORS. Wilmer A. Hoyer,

M'l BY I lord-S Tagged-Jr lnsulutor ATTORNEY.

United States 2,801,090 Patented July 30, 1957 SULFUR MINING USINGHEATING BY ELECTROLYSIS Wilmer A. Hoyer, Bellaire, and Millard S.Taggart, Jr., Houston, Tex., assignors, by mesne assignments, to EssoResearch and Engineering Company, Elizabeth, N. J., a corporation ofDelaware Application April 2, 1956, Serial No. 575,537

12 Claims. (c1. 262-3) The present invention is directed to the miningof liquefiable minerals contained in subsurface earth formations. Moreparticularly, the invention is directed to sulfur mining by means of awell bore penetrating a sulfurcontaining formation. In its more specificaspects, the invention is directed to the mining of sulfur without theuse of large amounts of water.

The present invention will be briefly described as a method forproducing liquefiable mineral from a subsurface earth formationcontaining the mineral and an aqueous electrolyte. In the practice ofthe present invention an electrode is placed in the formation in contactwith the electrolyte and an electric current is then passed through theelectrode and conducted through the electrolyte whereby the formation isheated by the electrical resistance of the electrolyte which causes theliquefiable mineral to be rendered fluid. The mineral is then flowedfrom the formation through a well penetrating the formation. Theliquefiable mineral is sulfur or crude petroleum which may be tooviscous to flow easily from the pores in the rock containing same.

The aqueous electrolyte employed in the practice of the presentinvention is either connate saline water which may be contained in theinterstices of the formation or may be a saline water introduced fromthe surface of the earth Where the electrical resistance of the connatewater is insuflicient to provide the amount of heat necessary to raisethe temperature of the formation to render the mineral liquefiable.

In the practice of the present invention, it is contemplated that aplurality of wells, such as five wells, may be drilled to penetrate theformation. One of the'wells surrounded by four of the wells may be usedas the producing well with the potential of selected wells beingcontrolled at subsubstantially the same potential such that currentflows from the producing well to the selected wells whereby theformation adjacent the producing well is heated to its maximum extent,the liquefied mineral being flowed from the producing well and, ifdesired, also from the selected wells.

In the practice of the present invention, it is contemplated, especiallywhere the liquefied mineral is sulfur, that air or other gasiformmaterial, such as inert gases and the like, may be introduced into thewell to aid or assist in lifting the fluid or liquefied mineral.

In the practice of the present invention a plurality of pipes arearranged in the well with one of the pipes being employed as anelectrode and other of the pipes being electrically insulated therefrom.To achieve this end, it may be desirable .to cement a well casing in thebore hole employing an electrical resistant cementing material, such asa high density Portland cement and the like, or a plastic material, suchas phenol-formaldehyde resin or ureaformaldehyde resin, and the like.

The several pipes which are arranged in the well are suitably insulatedelectrically above the point of contact at the lower end thereof witheach other and with the electrolyte to prevent current flow up the wellbore and the pipes.

The present invention will be further illustrated by reference to thedrawings in which:

Fig. 1 shows a schematic arrangement of a plurality of wells surroundinga producing well and the electrical connections therefor; and

Fig. 2 is a view taken along the lines II-Il of Fig. 1.

Referring now to the drawing, wherein identical numerals will bedesignated to designate identical parts, numerals 11, 12, 13 and 14designate boreholes drilled in the earths surface to penetrate asubsurface earth formation and numeral 15 designates a well which wasdrilled in the earths surface to penetrate the same formation surroundedby wells 11, 12, 13, 14. The wells 11, 12, 13, 14 and 15 are eachprovided, respectively, with electrodes 16, 17, 18, 19, and whichsuitably are pipes as will be described with respect to Fig. 2. Theelectrodes 16, 17, 18, 19, and 20 are each connected by electricalconnecting means 21, 22, 23, 24, and 25 to a source of electrical energyindicated by an A. C. generator schematically shown by numeral 26a, theelectrical connecting means 21, 22, 23, and 24 each containing a powerequalizer therein designated by the numerals 26, 27, 28, and 29 forcontrol of the electrical potential to the electrodes 16, 17, 18, and19. The electrical connection means 21, 22, 23 and 24 also have powermeters 30, 31, '32, and 33 in order to monitor the potential and thecurrent being applied to the several electrodes.

It is to be noted that each of the wells 11, 12, 13, 14, and 15 areprovided with insulators 34, 35, 36, 37,.and 38.

Referring now to Fig. 2 the wellbore 15 penetrates a subsurface earthformation 40 which is illustrated schematically as a sulfur-bearingformation which also contains limestone. The wellbore 15 has a casing 41arranged therein and a tubing 41a which is perforated in the formation40 by perforations 42. Arranged within the tubing 41a is a pipe string43 and arranged within the pipe string 43 is an inner pipe string 44.The casing 41 is cemented in the borehole 15 with a high density cement45 which fills the annulus 46 between the casing 41 and the borehole 15and also fills the annulus 47 between the casing 41 and the tubing 41a.The tubing 41a has, as indicated, perforations 42 and also is providedwith upper perforations 48.

The pipes 43 and 44 are provided with electrical contact means 49 and50, respectively, which suitably may be spring biased contact means toform an electrical contact between the pipe 44 and the pipe 43 andbetween the pipe 43 and the tubing 41a.

It is to be noted that the annulus 51 between the pipe 43 and the tubing41a is closed in by a packing means 52 and further it is to be notedthat the annulus 46 is closed in by a casing seat or other means 53cooperating with the cement 45. Also the annulus 47 is closed in by aclosure means 54 which serves to maintain the cement 47 in place untilit has set.

The casing 41 is provided with a plurality of insulators 55 and thetubing 41a is also provided with a plurality of insulators 56. The pipe43 also has a pluralityof insulators 57 The pipe 44 provides a conduitfor introducing compressed air into the well while the annulus 58between the pipes 43 and 44 serves as a passageway for molten sulfur.

The annulus 51 serves as a passagewayfor hot water which may be salinewater introduced into the well bore Bend the perforations 48.

In practicing the present invention, especially with reference to Fig.l, a five-spot plan of wells is drilled in the earths surface with thewell 15 being the producing 3 well. The flow of current from thegenerator 26 is started and the potential is adjusted by the powerequalizers so that the voltage drop is from'the producing well 15 to theperipheral wells 11, 12, 13 and 14 which allows the formation 40 to beheated most adjacent the producing well 15. Thus electrical'current isconducted from the center pipe 44 through the contact 50' to the pipe 43and thence by the contact 49 to the tubing 41a which serves as anelectrode. The wellbore 15 contains saline water which serves as anelectrolyte and the formation'40 also contains saline water. Since thecurrent is carried by the electrolyte and since the electrolyte has ahigher resistance as compared to the metallic conductors, an appreciableamount of heat is produced in the formation. By continuing to apply thecurrent to the system, as shown-in Fig. l, the formation 40'is heated toa point that the sulfur contained therein is liquefied and flows in thedirection of the borehole and is lifted to the surface by theairintroduced through ,pipe 44.

will yield a temperaturerise in'a 40 acre section 300 feet thick of 1"F. for every 9.8 days. p l H The presentinvention has'great utility andadvantages since it is no longer necessary to use hot water in themining of sulfur since in the Frasch process molten sulfur must runcountercurrent' to the flow of water to reach the Wellbore. In suchoperations, the sulfur may be forced ahead of the water and be lost.Also the prior arts'ulfur mining processes requiring large volumes ofwater raise .the formation pressure to dangerous levels and require thedrilling of expensive wells to bleed off the pressure. Suchdisadvantages are obviated in the practice of the present inventionsince the heat required to melt .the sulfur is produced 'by passing theelectric current'thr'ough an appreciable horizontal section of theprodu'cing formation. In this connection, the wells may be spacedfrom'about 100 to about 1500 feet apart and yet realize the advantagesof the present invention. 7 The'present invention has numerousadvantages over resistance of the-electrolyte is introduced only intothe ore body and large bodies of hot water are not required and,therefore, will not be lost into distant parts of the caprock; Also themolten sulfur may flow to the well without interference of acountercurrent flow of 'hot water. In the practice of the presentinvention, formation pressures are not raised to dangerous levels andalso auxiliary Wells to bleed off pressure are not required.

The present invention'is, therefore, quite useful.

in viscous bodies of crude petroleum are contained in rock and the like.

The nature and objects of the present invention having been completelydescribed and illustrated, what We wish to claim as new and useful andto secure by Letters Patentis:

1. A method for producing aliquefiable mineral from a subsurface earthformation containing said mineral and an aqueous electrolyte whichcomprises drilling a well to penetrate said formation, placing anelectrically insulated pipe in said well, placing a plurality ofelectrodes in said formation surrounding said'well; and in contact withsaid electrolyte, passing an electric current through said electrodesand the insulated pipe'and conducting said current through saidelectrolyte, the input current to selected of said electrodessurrounding said well and to said insulated pipe being controlled suchthat current flow is from the well to said selected electrodes, wherebysaid formation is heated to its maximum extent adjacent the well by theelectrical resistance of said electrolyte and said mineral is renderedfluid, and then flowing said mineral from said formation through saidwell penetrating the formation. a

2. A method in accordance with claim 1 in which the mineral is sulfur. 1

3. A method in accordance with claim 1 in which the a aqueouselectrolyte is saline water introduced into the formation.

f 6. A method for producing a liqueiiable mineral from a .subsurfaceearth fonnationrcontaining said mineral and an aqueous electrolyte whichcomprises drilling a' plurality of wells to penetrate said formation,placing an electrically insulated pipe in each of said wells in. contact1 with said electrolyte, passing anelectric current through J theproducing Well to said selected .wells whereby the the prior artprocesses in that the heat by the electrical formation is heated to itsmaximum extent adjacent the producing well by the electrical resistanceof said electrolyte and said mineral is rendered fluid, and then flowingsaid'mineral from said formation at least through said producing well.

7. A method in accordance with claim 6 in which a gasiform medium underpressure is injected into at least said producing well to assist inlifting the fluid mineral. 8. A method in accordance with claim 6 inwhich the mineral is sulfur.

' 9. Amethod in accordance with claim 6 in which the mineral is crudepetroleum.

10.. A method in accordance with claim 6 in which saline water isintroduced into said formation to provide said electrolyte.

, ll. Amethod in accordance with claim 6 in which a casing is cementedinto each ofsaid wells, prior to placing said pipes, with an electricalresistant cementing material. 12. A method in accordance with claim 6 inwhichthe l aqueous electrolyte is connate'saline'water;

eral, the heating will take place in the mineral-containing rock bytheelectrical'resistanc'e of the water therein.

While the present invention has been described primarily'with respect tothe production of sulfur, it is equally applicable to the production ofcrude oil where- References Cited in the file of this patent UNITEDSTATES PATENTS 849,524 1,372,743 'Gardner Mar. 29, 1921 1,784,214Workman Dec. 9, 1930 2,761,829 Dolloif Sept. 4, 1956 Baker Apr. 9, 1907

1. A METHOD FOR PRODUCING A LIQUEFIABLE MINERAL FROM A SUBSURFACE EARTHFORMATIOON CONTAINING SAID MINERAL AND AN AQUEOUS ELECTROLYTE WHICHCOMPRISES DRILLING A WELL TO PENETRATE SAID FORMATION, PLACING ANELECTRICALLY LIN SAID FORMATION SURROUNDING SAID WELL AND IN CONTACTWITH SAID ELECTROLYTE, PASSING AN ELECTRIC CURRENT THROUGH SAIDELECTRODES AND THE INSULATED PIPE AND CONDUCTING SAID CURRENT THROUGHSAID ELECTROLYTE, THE INPUT CURRENT TO SELECTED OF SAID ELECTRODESSURROUNDING SAID WELL AND TO SAID INSULATED PIPE BEING CONTROLLED SUCHTHAT CURRENT FLOW LIS FROM THE WELL TO SAILD SELECTED ELECTRODES,WHEREBY SAID LFORMATION IS HEATED TO ITS MAXIMUM EXTENT ADJACENT THEWELL LBY THE ELECTRICAL RESISTANCE OF SAID ELECTROLYTE AND SAID MINERALIS RENDERED FLUID, AND THEN FLOWING SAID MINERAL FROM SAID FORMATIONTHROUGH SAID WELL PENETRATING THE FORMATION.